1. Technical Field
This invention relates generally to seat hinge mechanisms for folding-type vehicle seats and, more particularly, to such a seat hinge mechanism having an inertia-sensitive latch assembly which permits the seatback to be folded forward during normal use but which locks to prevent folding when the vehicle is subjected to deceleration forces exceeding a predetermined threshold level.
2. Discussion
Most two-door passenger-type motor vehicles have a rear seat area or luggage compartment area that is accessible by forwardly pivoting or folding a seatback portion of the front seat. Current U.S. Federal Motor Vehicle Safety Standards require the front vehicle seat to be equipped with a latching mechanism for inhibiting forward rotation of the foldable seatback when deceleration forces exceed a predetermined threshold level which may occur, for example, during an emergency heavy braking condition or a frontal collision.
In the past, the seat hinge mechanisms associated with some folding-type vehicle seats were provided with a manually-activated seatback latching mechanism. As an alternative, other seat hinge mechanisms incorporate an inertia-sensitive latching mechanism which enables a seatback to be folded forward without significant resistance when the vehicle is not subject to the above-mentioned predetermined deceleration forces. However, when the predetermined deceleration forces are present, the inertia-sensitive latching mechanism is activated for latching the seat hinge mechanism to prevent forward pivotal movement of the seatback.
In many commercially available vehicle seating arrangements, the inertia-sensitive type seat hinge mechanism further provides a mechanism for positioning the inertia-sensitive actuator or element in an engaged position when the seatback is folded to its rearmost position. For such mechanisms, the inertia-sensitive actuator is free to move between engaged and released positions once the seatback is folded several degrees forward. When deceleration loads above the predetermined level are present, the inertia-sensitive actuator remains in an engaged position, thus preventing forward rotation of the seatback. Such seat hinge mechanisms cause the inertia-sensitive element to be continuously moved between its engaged and released positions, thereby reducing the likelihood that corrosion, foreign matter, etc. will interfere with the free movement thereof.
A known disadvantage associated with many conventional seat hinge mechanisms having the above-discussed features, is that they present an edge surface which protrudes toward the rear seat area when the front seatback is rotated forward. Thus, the rear seat occupants could possibly contact the protruding edge surface while entering or egressing the rear seat area. Accordingly, it is desirable to provide a seat hinge mechanism which does not interfere with access to the rear compartment area. In addition to the above, seat hinge mechanisms having an inertia-sensitive latching device are required to have an emergency release that is operable to release the inertia-sensitive actuator, thereby enabling a rear seat occupant to escape from the vehicle by releasing the seatback in an emergency situation. Emergency releases typically include a manually-operable lever which forcibly displaces the inertia-sensitive actuator into the released position. Since the emergency release must be accessible to the rear seat occupant, the emergency release lever typically protrudes rearwardly from the seatback. In order to simplify trimming of the seatback, it is desirable to locate the emergency release lever at a position near the hinge or pivot between the seatback and the seat bottom.
Another disadvantage associated with conventional seat hinge mechanisms having the above-discussed features is that they require the seatback to be lifted and the emergency release lever to be actuated simultaneously to forwardly pivot the seatback. Such actuation requires a passenger to use both hands which can be inconvenient or impossible, especially during emergency situations. Therefore, a hinge mechanism incorporating an inertial latching mechanism which releases by raising the emergency release lever without also lifting the seatback is desirable.
Although inertia-sensitive seat hinge mechanisms incorporating some of the above-noted features are commercially available and perform satisfactorily for this intended purpose, a need exists to provide continuous improvement in this field of technology for reducing overall system complexity and cost while concomitantly enhancing operational reliability and durability.